Cathode ray control apparatus



Oct. 22, 1957 R. G. MORK CATHODE RAY CONTROL APPARATUS 3 Sheets-Sheet '1 Filed July 2, 1956 BN m Emma Ec A Ec RR fiRR c c fiwuw Uw WC 2 WCCS S 1 s .m mm

GN OI\J IN ml 1 DI INVENTOR.

RALPH G. MORK AGENT O 1957 R. e. MORK 2,8

a V CATHODE RAY CONTROL APPARATUS 7 Filed July 2, 1956 v 3 Sheets-Sheet 2 Deflection Circuitry X DIGITAL INPUT IIIIIIIF Oct. 22, 1957 R. G. no 2,810,860

CATHODE RAY CONTROL APPARATUS Filed July 2', 1956 3 Sheets-Sheet 3 Circuitry INPUT United States. Patent 2,810,860 CATHODE RAY CONTRQL APPARATUS Ralph G. Mork, Vestal, N. Y., assignor to International Business Machines Corporation, New York, N. Y., a

corporation of New York Application July 2, 1956, Serial No. 595,477 14 Claims. (Cl. 31527) This invention relates to an arrangement for controlling the deflection of the beam of electrons in a cathode ray tube.

The present invention is more particularly directed to a system for magnetically controlling the deflection of an electron beam in accordance with digital information such as would be obtained from a digital computer or the like. The present system preferably makes use of a magnetic deflection yoke having a push-pull winding in its X axis and in its Y axis. The digital input information in the form of binary coded pulses is fed in parallel fashion to a group of switching tubes. The switching tubes accordingly connect certain selected binary weighted constant current sources into the yoke windings which results in a deflection of the electron beam to a position corresponding to the digital input data. Such a systemtor driving a deflection yoke has the advantage of a reduc tion in the amount of equipment required, particularly, the elimination of feed-back D. C. amplifiers. It has the further advantages of less likelihood of drift and rapid response time.

A main object of the present invention is to provide an improved magnetic deflection system for an electron beam.

example, the principle of the invention and the best mode,

which has been contemplated, of applying that principle.

in the drawings: Fig. 1 is a schematic diagram of the system. Fig. 2 is an isometric diagram of a deflection coil-struc' ture for controlling the deflection of the electron beam. Fig. 3 is a schematic circuit diagram showing the coils of the coil structure connected in series.

Fig. 4 is a circuit diagram showing one embodiment of the novel driving circuitry for the deflection yoke employing a fixed voltage source for determining the switching level.

Fig. 5 is a circuit diagram showing a second embodiment of the novel driving circuitry for the deflection yoke employing a push-pull trigger arrangement for controlling the switching.

In the present system, as shown schematically in Fig. 1, the digital input data, indicated by .blocks and 11,

for causing deflection of the electron beam along the X and Y axes of the cathode ray tube C is fed in parallel to control respective switching circuitry. The respective switching circuit sections, indicated by blocks 12 and 13, in turn supply values of current to the deflection yoke windings 14 through 21.

The system preferably makes use of the well-known type of deflection yoke having push-pull windings in its X axis and in its Y axis and such a yoke is fully disclosed in U. S. Patent No. 2,395,966, to which reference 2,8103% Patented Get. 22, 1957 may be had for complete details of operation. Therefore, only those details of the yoke construction will be set forth here as is believed necessary to understand the application of the novel driving circuitry to be later described. I

The yoke is wound with eight coils having equal numbers of turns and arranged as four coaxial pairs as shown in Fig. 2. These coils may be connected in series as shown in Fig- 3. IThe arrows indicate the sense of the coil, considering fluxes as set up in the core. 14 and 15 on the upper leg of the coil core begin at a and b, respectively, and end at a and b, respectively, as shown in Fig. 2 and are concentrically wound. Similar pairs of concentric windings are arranged on the other three core legs. Since all four sets of coils are symmetrical, equal steady state components of the currents supplied will produce fields which cancel and produce no deflections. Any differences in the currents in pairs, however, result in a deflection.

For the sake of brevity, it is believed unnecessary to show the internal construction or to describe the principle of operation of the cathode ray tube, since these tubes are widely used in various electrical systems and radio applications, there being several forms available. Furthermore, this invention relates to a method for producing beam deflection, by the electromagnetic method, and in particular to improved circuit means for generating currents in the coil windings for providing the magnetic field to give a deflection corresponding to the value of the digital input data. As an example of one application, the present system may be used to deflect the beam onto a character matrix to place on the screen of the cathode ray tube the characters which are representative of the input data.

Referring to Fig. 4, there is shown one form of the improved circuitry for converting parallel digital information to a corresponding current in the coils of the deflection yoke. The circuit comprises four triode tubes V1, V2, V4 and V8 which act as constant current sources. The value of constant current generated by each of these tubes is determined by a constant voltage source E1 and by the cathode resistor associated with each tube. The current in each of the four constant current sources is adjusted by varying the value of the cathode resistor in eachsource and for purposes of illustration the references R1, R2, R4 and R8 have been used to indicate a binary weighing, for example, the current source V1 would supply 1 milliampere, V2 would supply 2 milliamperes, V4 4 milliamperes and V8 8 milliamperes. The choice of current used in a particular system would of course depend on the sensitivity of the deflection yoke. Furthermore, other codings could be used in lieu of the straight binary code indicated. Although only four digital inputs have been shown it is perfectly feasible to increase this number to any desired quantity by the addition of one constant current tube and a pair of switch tubes for each additional bit, as will be understood.

Connected between the plates of the constant current tubes and the coils of the deflection yoke are two groups of switching tubes. The switching tubes operate in parallel into the push-pull windings of the yoke, the lefthand group of switching tubes Via, V2a, V411 and V811 operating the X deflection coils 18 ad 20 and the righthand group of switching tubes Vlb, V2b, V4b and V8b operating the X deflection coils 19 and 21. It is to be noted that pairs of switch tubes operate through a com mon constant current tube, for example, switch tubes Vla and Vlb operate through the constant current tube V1. Switch tubes VZa and V2!) operate through the constant current tube V2 and so on. The digital inputs to the X deflection circuitry are shown as binary code The two windings pulses which feed into the grids of the right-hand switch tubes V1bV8b and a fixed voltage source indicated as E2 is provided common to the grids of the left-hand switch tubes VItaV8a to determine the switching level.

In operation the digital inputs are voltage levels wherein, for example, a binary zero would be represented by a voltage sufficiently less than E2 to cause the right-hand switch tubes to be cut off. To illustrate a set of voltage conditions which may be applied to operate the circuitry assume that the B+ plate voltage is approximately 300 volts, the E1 and E2 voltage sources at 50 and 100 volts, respectively, and the cutoff bias voltage of the switching tubes at 10 volts negative or, in other words, positive 90 volts. For selected values of tube characteristics and resistances, the left-hand switching tubes V1aV8a will be conducting current from the constant current sources due to the positive 100 volt potential on the grids and the IR drop across the constant current tube V1 and resistance R1, for example, would place the cathodes of the pair of switching tubes Vla and Vlb somewhere around 103 volts[ With a binary O voltage level set at 90 volts, for example, a binary pulse fed into the grid of switch tube Vlb places the grid 13 volts negative with respect to its cathode potential or below cutoff and tube Vlb does not conduct. Hence, for a binary 0 on each digital input 'all.

current from the constant current sources passes through the switch tubes V1a-V8a into the push-pull windings 18 and 20.

In similar fashion a binary 1 is represented by a voltage level on the digital inputs sufliciently greater than E2 to cause the left-hand group of tubes V1aV8a to switch to cutoff causing all of the current from the constant current sources to pass through the right-hand switch tubes V1b-V8b into the push-pull windings 19 and 21. For example, with a binary l voltage level set at 110 volts a binary 1 fed into the grid of Vlb causes tube Vlb to now conduct. The potential at the cathodes of Vla and Vlb will now increase to around 113 volts and consequently tube Via with its grid at 100 volts will be biased below cutofl.

Since the action of each switch tube pair is independent of all other switch tubes and since a separate constant current source is provided for each pair of switch tubes, the total current flowing through each half of the pushpull windings is entirely dependent upon the combination of l or O voltage levels present on the digital input,

lines and is also dependent upon the setting of each of the constant current tubes.

The Y deflection circuitry, indicated by the block 22, is identical in construction and operation to the X deflection circuitry just described and hence it was deemed unnecessary to duplicate a detail showing and description of same.

In Fig. 5 there is shown a second embodiment of the system wherein the pairs of switching devices are all operated directly from trigger outputs. Such an arrangement has a practical advantage in that it does not require a separate source of voltage for determining the switching level of the switching devices.

The blocks indicated as T1, T2, T4 and T8 represent the well-known trigger or flip-flop circuitry which operates in binary fashion and it is not believed necessary to discuss the operation or show the details of the trigger circuit itself. Suffice it to say that in representing a binary 0 a trigger is considered in the off state with the right side of the trigger conducting and the 0 output terminal positive relative to the 1 output terminal. For example, the 0 terminal may be at 100 volts and the 1 terminal at volts. Conversely, in representing a binary l a trigger is considered in the on state with the left side of the trigger conducting and the 1 output terminal positive relative to the 0 output terminal.

In the embodiment shown in Fig. 5 the 0 output terminal of each trigger is connected to the grid of a related one of the switch tubes Vla-VSa and likewise the 1 output terminal of each trigger is connected to the grid ofa related one of the switch tubes V1bV8b. The connections between the switching tubes, the push-pull windings and the constant current sources are the same as previously described. It can be readily understood then, that when the triggers represent a binary 0 the potential volts) at the grids of the tubes Vla-V8a will be substantially more positive than the potential (50 volts) at the grids of tubes V1bV8b resulting in tubes V1a-V8a conducting and the tubes Vlb-V8b to be cut off. Consequently, as in the previous case, for a binary 0 all current from the constant current sources V1V8 pass through the switch tubes V1aV8a into the pushpull windings 18 and 20.

In: similar-fashion with each trigger representing a binary l the grids of the tubes V1bV8b will be at a greater potential and these tubes will be conducting while tubes VlaV8a will be cut off All of the current from the constant current sources will now pass through the switch tubes V1l1V8b into the push-pull windings 19 and 21.

As before, the action of each switch tube pair is independent of all other switch tubes and since a separate constant current source is provided for each pair of switch tubes, the total current flowing through each half of the push-pull windings is entirely dependent upon the combination of 0 and l potentials present at the output terminals of the triggers.

The ,Y deflection circuitry, indicated by the block 23 (Fig. 5), is identical in construction and operation to the X deflection circuitry last described and hence it was deemed unnecessary to duplicate a detail showing and description of same.

It is to be understood that the invention is not limited to the use of a push-pull type of yoke. For example, a single ended yoke; in other words, a yoke as shown in Figs. 2 and 3 with the coils 15, 17, 19 and 21 removed, couldv be used. The electron gun in the cathode ray tube could be aimed olf axis so that the beam would strike near the edge of the screen, say in the lower left-hand corner, with no current in the yoke. The beam can then be deflected in one direction along the X and Y axes. In both embodiments shown in Figs. 4 and 5, for example, the windings l9 and 21 could be removed and the plates of the switch tubes V1b-V8b connected directly to the B+ plate voltage. Of course, using a single ended yoke would require that the constant current sources provide double the amount of current needed for push-pull operation.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. A system for converting coded pulses to a corresponding current in a cathode ray tube deflection yoke comprising, push-pull windings on said yoke, a source of voltage, a plurality of constant current sources connected across saidvoltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs having consecutive values following a predetermined code, switching means connecting each output of said constant current sources with one half of said pushpull windings, second switching means connecting each output of said constant current sources with the other half of said push-pull windings, and control means for operating said switching means ,to transmit individual current out- Puts fIOmsaid constant current sources to either half of 5 said push-pull windings depending upon the patterns said coded pulses. a

2. A system for converting binary coded pulses to a corresponding current in a cathode ray tube deflection yoke comprising, push-pull windings on said yoke, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant cur-rent sources for effecting current outputs having consecutive values following a predetermined code, switching means connecting each output of said constant current sources with one half of said push-pull windings, second switching means connecting each output of said constant current sources with the other half of said push-pull windings, and control means for operating said switching means to transmit individual current outputs from said constant current sources into one half of said push-pull windings for binary O pulses and into the other half of said push-pull windings for binary 1 pulses.

3. A system for converting coded pulses to a correpding current in a cathode ray tube deflection yoke comprising, push-pull windings on said yoke, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs having consecutive values following a predetermined code, switching means connecting each output of said constant current sources with one half of said push-pull windings, second switching means connecting each output of said constant currentsources with the other half of said push-pull windings, input connections between said coded pulses and said first switching means, a second voltage source for determining the switching level of said switching means, and connections between said second voltage source and said second switching means, said switching means operating to transmit individual current outputs from said constant current sources to either half of said push-pull windings depending upon the patterns of said coded pulses.

4. A system for converting coded pulses to a corresponding current in a cathode ray tube deflection yoke comprising, push-pull windings on said yoke, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs having consecutive values following a predetermined code, a first group of switching devices the outputs of which are connected to one half of said push-pull windings, a second group of switching devices the outputs of which are connected to the other half of said push-pull windings, means connecting the input sides of corresponding switching devices from each group to form pairs of switching devices, means connecting the input of each pair of switching devices to the output of a related one of said constant current sources, and control means for efiecting operation of one switching device of each pair to transmit individual current outputs from said constant current sources to either half of said push-pull windings depending upon the patterns of said coded pulses.

5. A system for converting coded pulses to a corresponding current in a cathode ray tube deflection yoke comprising, push-pull windings on said yoke, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs having consecutive values following a predetermined code, a first group of electron switching devices each having at least an anode, a cathode and a control electrode, connections between the anodes of said first group of switching devices and one half of said push-pull windings, a second group of electron switching devices each having atleast an'anode, a cathode and a control electrode, connections between the anodes of said second group of electron switching devices and the other half of saidpush-pull windings, connections between the cathodes of corresponding switching devices from each group to form pairs of switching devices, a common connection between the cathodes of each pair ofswitching devices and the output of a related one of said constant current sources, a second voltage source having a common connection with the control electrodes of one of said groups of switching devices for determining the switching level of the switching devices, and input connections between said coded pulses and the control electrodes of the other group of switching devices, said switching devices operating to transmit individual current outputs from said constant current sources to either half of said push-pull windings depending upon the patterns of said coded pulses.

6. A system for converting coded pulses having different voltage levels to a corresponding current in a cathode ray tube deflection yoke comprising, push-pull windings on said yoke, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs having consecutive values following a predetermined code, a first group of electron switching devices each having at least an anode, a cathode and a control electrode, connections between the anodes of said first group of switching devices and one half of said push-pull windings, a second group of electron switching devices each having at least an anode, a cathode and a control electrode, connections between the anodes of said second group of electron switching devices and the other half of said push-pull windings, connections between the cathodes of corresponding switching devices from each group to form pairs of switching devices, a common connection between the cathode of each pair of switching devices and the output of a related one of said constant current sources, a second voltage source having a predetermined voltage level and having a common connection with the control electrodes of one of said groups of switching devices for determining the switching level of the switching devices, and input connections between said coded pulses and the control electrodes of the other group of switching devices, said code pulses having either a voltage level less than the voltage level of said voltage source to eflect operation of said switching devices to transmit individual current outputs from the related constant current sources to one half of the push-pull windings or a voltage level greater than the voltage level of said voltage source to effect operation of said switching devices to transmit individual current outputs from the related constant current sources to the other half of the push-pull windings.

7. A system for converting coded pulses having dilferent voltage levels to a corresponding current comprising, push-pull windings, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs having consecutive values following a predetermined code, a plurality of pairs of electron switching devices, each pair of switching devices connecting the output of a related constant current source to either half of said push-pull windings, a source of voltage for maintaining said pairs of switching devices at a predetermined switching level, and input connections between said coded pulses and said pairs of switching devices for effecting operation of said switching devices to transmit individual current outputs from said constant current sources to either half of said pushpull windings depending upon the voltage levels of said coded pulses.

8. A system for converting coded pulses having difierent voltage levels denoting a binary O or a binaryl to a.

corresponding current comprising, push-pull windings, a source of voltage,.a plurality of constant current sources connected across said voltage source and corresponding in number to the numberof digits in said code, control means for each of said constant current sources for effecting current outputs havingconsecutive values followinga predetermined code, a plurality of pairs of electron switching devices, each pair of switching devices connecting the output of a related constant current source to either half of said push-pull windings, a source of voltage for maintaining said pairs of switchingdevices at a predetermined switching level, and input connections between said coded pulses and said pairs of switchingdevices for effecting operation of said switching devices to transmit individual current outputs from said'constant sources to one half of said push-pull windings for binary pulses and to the other half of said push-pull windings for binary l pulses.

9. A system for converting coded pulses having different voltage levels to a corresponding current comprising, push-pull windings, a source of voltage, a-plurality of constant current sources connected across said voltage source and corresponding in number to the number of.

digits in said code, control means for'each ofsaid constant current sources for effecting current outputs having consecutive values following a predetermined code, a plurality of pairs of electron switchingdevices, each pair of switching devices connecting the'output of a .related constant current source to, either half of said push-pull windings, a source of voltage for maintaining said pairs of switching devices at a predetermined switching level with a corresponding side of each pair ina normally conductive state, and input connections between said coded pulses and said pairs of switching devices for efiecting operation of said switching devices to transmit individual current outputs from said constant current sources to one half of said push-pull windings for those pulses having a voltage level less than said switching level, said devices operating to switch said current outputs to the other half of said push-pull windings for those pulses having a voltage level greater than said switching level.

10. A system for converting coded pulses to a corresponding current comprising, push-pull windings, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs havin consecutive values following a predetermined code, a plurality of pairs of electron switching devices, each pair of switching devices connecting the output of a related constant current source to either half of said push-pull windings, a plurality of electron trigger devices each having a state of conduction to represent a digit in said code, and connections between each trigger device and a related pair of switching devices, said switching devices operating to transmit individual current outputs from said constant current sources to either half of said push-pull windings depending upon the conductive pattern of said trigger devices.

11. A system for converting coded pulses to a corresponding current comprising, push-pull windings, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control means for each of said constant current sources for effecting current outputs having consecutive values following a predetermined code, a plurality of pairs of electron switching devices, each pair of switching devices connecting the output or" a related constant current source to either half of said push-pull windings, a control electrode for each.

switching device, a plurality of electron trigger devices each having a state of conduction to represent a digit in said code, a pair of output terminals for each trigger de: vice, and connections between corresponding output ter-,.

minalsof said trigger'devices and the control electrodes: of corresponding switching devices of each-v pair said switching devices operatingto transmit individual current outputs from said constant current sources to either half: of said push-pull windings depending upon the conductive. pattern of said trigger devices.

12. A system for converting coded pulses having different voltage levels denoting a binary 0 or a binaryl to a corresponding current comprising, push-pull windings, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said code, control -.means-foreacl1 of said constant current sources for effecting currentoutputs having consecutive values following a predetermined code, a first group of electron switching devices connecting each output of said constant current sources with one half of said push-pull windings, a second group of electron switching devices connecting each output of. said constant current sources with the other half of said push-pull windings, control electrodes for each of said switching devices, a plurality of electron trigger devices each having a state of conduction to representa binary 0 or a binary l in said code, a binary 0-and a binary 1 output terminal for each trigger device,v connections between the binary 0 terminals and the control electrodes of said first group of switching devices, and connections between the binary 1 terminals-and the control electrodes of said second group of'switching devices, said switching devices operating totransmit individual current outputs from said constant current sources to either half of said push-pull windings depending upon the conductive pattern of said trigger devices.

13. A system for converting coded pulses having different voltage .levels to a corresponding current comprising,- single ended windings, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number to the number of digits in said v code, control means for each of .said constant current sources for effecting current outputs having consecutive values following a predetermined code, a plurality of pairs of electron switching devices, a source of supply voltage for said switching devices, each pair of switching devices connecting the output of a related constant current source either to said windings and supply voltage or directly to said supply voltage, a source of voltage for maintaining said pairs of switching devices at a predetermined switching level, and input connections between said coded pulses and said pairs of switchingdevices for effecting operation of said switching devices to transmit individual current outputs from certain of said constant current sources to said windings depending upon the voltage levels of said coded pulses.

14. A system for-converting coded pulses to a corresponding current comprising, single ended windings, a source of voltage, a plurality of constant current sources connected across said voltage source and corresponding in number'to the number of digits in said code, control means for each of said constant current sources foreifecting current outputs having consecutive values following a predetermined code, a plurality of pairs of electron switching devices, a source of supply voltage for said switching devices, each pair of switching devices connecting the output of a related constant current source either to. said windings and supply voltage or directly to said supply voltage, a plurality of electron trigger devices each having a state of conduction to represent a digit in said code, and connections between each trigger device and a related pair of switching devices, said pairs of switching devices operating to transmit individual current outputs from certain of said constant current sources to. said windings depending upon the conductive pattern of said trigger devices.

No references cited." 

